The invention relates to a method and a system for forwarding emergency messages in a communication network, especially for WiMAX networks.
In order to stimulate a new wireless communication technology for mobile terminals, which also achieves longer ranges of up to 30 km or more (line-of-sight) with high data throughput rates of 75 MB/s, a plurality of interested parties have joined together in the so-called WiMAX Forum (www.WiMAXforum.org). WiMAX (Worldwide Interoperability for Microwave Access) provides three frequency bands around 2.6 GHz, 3.5 GHz and 5.8 GHz with frequency bandwidths of 100 to 200 MHz. WiMAX supports Mobile-IP (Internet protocol) and thus enables mobile terminals to make telephone calls via Voice-over-IP with other communication users for example.
A requirement of future WiMAX networks is that, in addition to the existing services, they also support emergency services. The emergency services are intended to guarantee that a user is able, even without valid registration, to transmit emergency messages to the selected communication network.
No valid registration at the communication network exists unless the user possesses an appropriate key for authentication at the visited communication network. This is for example the case if the communication user has not registered with the respective network operator for the visited communication network or the network operator with which the communication user has negotiated a registration has no roaming agreement with the communication network now being visited.
A further possible reason for the absence of a valid registration at a communication network is when the prepaid account of the relevant communication user is empty or not sufficiently topped up.
Usually a terminal or its communication user are authenticated in accordance with the related art by an Authentication Authorization and Accounting Client (AAA Client) in the Access Serving Network (ASN) submitting a request message for authentication to the authentication server in the home network Connectivity Service Network (CSN). To this end a Network Access Identifier (NAI) is transferred in the authentication message of the terminal to the authentication server in the access network. The network access identifier features a character string for identification of the Network Service Provider (NSP), in which the relevant communication user has undertaken a registration. In addition the message usually contains a character string to identify the user. Based on the network access identifier and the information that it provides about the network service provider, the authentication server in the home network of the communication user will be found. In the event of a valid registration at a communication network not being available, access remains refused to the communication user. In such a case it is also not possible for the communication user to make emergency calls.